goma: use GOMA_SERVICE_ACCOUNT_JSON_FILE (reland #1)

scripts/slave/compile.py

Index: scripts/slave/compile.py
diff --git a/scripts/slave/compile.py b/scripts/slave/compile.py
index 9673be4c3448feeee11f0f618fc776c94675dd3b..3a4eba45dcf4842a2c600dcdc62764ca2bb48346 100755
--- a/scripts/slave/compile.py
+++ b/scripts/slave/compile.py
@@ -177,6 +177,9 @@ def goma_setup(options, env):
   goma_key = os.path.join(options.goma_dir, 'goma.key')
   if os.path.exists(goma_key):
     env['GOMA_API_KEY_FILE'] = goma_key
+  if options.goma_service_account_json_file:
+    env['GOMA_SERVICE_ACCOUNT_JSON_FILE'] = \
+        options.goma_service_account_json_file
   if chromium_utils.IsWindows():
     env['GOMA_RPC_EXTRA_PARAMS'] = '?win'
   goma_start_command = ['restart'] if options.clobber else ['ensure_start']
@@ -1265,6 +1268,9 @@ def real_main():
   option_parser.add_option('--goma-disable-local-fallback', action='store_true')
   option_parser.add_option('--goma-jsonstatus',
                            help='Specify a file to dump goma_ctl jsonstatus.')
+  option_parser.add_option('--goma-service-account-json-file',
+                           help='Specify a file containing goma service account'
+                                ' credentials')
   option_parser.add_option('--verbose', action='store_true')
   option_parser.add_option('--gsutil-py-path',
                            help='Specify path to gsutil.py script.')